ASTER 257 



(y) Heads fewer in a narrow spike-like 

 cluster 

 m. Stems and involucres white-felted A. Wrightii 

 n. Stems and involucres hairy to 



smooth A. bar calls 



Aster Linne 1753 Aster 



(Gr. aster, star) 



PI. 3$, fig. 5. 



Heads with white, pink, bine, violet or purple pistillate ray-flowers, 

 disk-flowers yellow, becoming brown, purple or red, perfect, achenes usu- 

 ally flattened and nerved, pappus of hair-like bristles ; receptacle flat to 

 convex, without chaff, involucre hemispheric to top-shaped, the bracts usu- 

 ally unequal and imbricated in several rows, sometimes about equal and 

 in 2-3 rows ; heads solitary or in corymbs or panicles ; leaves alternate, 

 simple ; perennial or rarely annual. 



1. Annuals 



a. Bracts linear or linear-lanceolate, pointed A. angustus 



b. Bracts oblong to oblanceolate, blunt or rounded A. frondosus 



2. Perennials 



a. Bracts spiny -pointed ; stems tufted, 1-headed 



(1) Leaves not spiny-toothed, spatulate or 



oblanceolate; heads 10-15 mm. wide; 



rays white A. villosus 



(2) Leaves spiny-toothed, spatulate; heads 10- 



12 mm. high; rays purple A. coloradensis 



b. Bracts not spiny-pointed 



(1) Bracts broad with keel-like midrib, papery, 



usually fringed and purple-tipped 



(a) Involucres 12-20 mm. wide; leaves 



mostly 1.5-2.5 cm. wide A. Engelmdnull 



(b) Involucres 6-10 mm. wide; leaves usu- 



ally less than 1 cm. wide 

 x. Stems usually simple ; bracts purple, 



acute A. elcgans 



y. Stems usually much branched ; bracts 



scarcely purple, outer rounded or 



blunt A.glaucus 



(2) Bracts mostly narrow, without keel-like 



midrib 



